Many chemotherapeutic agents and antibiotics have been evaluated for prevention and treatment of swine dysentery, and certain synthetic antimicrobial agents in the quinoxaline, nitroimidazole and nitrofuran series and antibiotics in the macrolide and diterpene series have been put to use. Prophylactic methods using vaccines have also been investigated but none have been developed to the practically useful stage as yet. Thus, chemotherapeutics and antibiotics are playing leading roles in the prophylaxis and treatment of swine dysentery today.
Swine dysentery is an infectious disease in pigs which is principally caused by Treponema hyodysenteriae, large spirochaete, and its chief manifestations are mucohemorrhagic diarrheal stools. This epidemic in swine herds is slow to spread as compared with other acute infections but as a huge number of organisms are contained in their feces, the surroundings are quickly contaminated and it is acknowledged to be extremely difficult to clean the swine quarters where this epidemic has once taken hold.
The long-term losses to the feeder pig producer due to the growth retardation and decreased feed conversion induced by swine dysentery are uncalculably great. While the aforementioned drugs have been used just for the purpose of avoiding such losses, their effects are not necessarily satisfactory.
Regarding hygromycin, R. C. Pittenberg et al. discovered it in a culture of Streptomyces hygroscopicus in 1953 and reported for the first time its antimicrobial spectrum and the results of their infection study [Antibiotics Annual, 1953-1954, P. 157]. Then, in 1957, R. L. Mann et al. determined its chemical structure [Journal of The American Chemical Society, 79, 120 (1957)]. It was also shown that Streptomyces atrofaciens produces the same substance (U.S. Pat. No. 3,100,176; Aug. 6, 1963). On the other hand, Sumiki et al. reported on the antituberculous antibiotic homomycin produced by Streptomyces noboritoensis as an analog of hygromycin [Journal of Antibiotics, Series A, 8, 170 (1955)]. However, the subsequent comparative study of this antibiotic and hygromycin by K. Isono et al. showed that the two antibiotics are actually the same substances [Journal of Antibiotics 10, 21 (1957)]. More recently, ST-4331 reported by K. Kakinuma et al. was identified with hygromycin and its absolute structure was presented [ Journal of Antibiotics, 29, 771, (1976)]. However, Wakisaka et al. corrected the suggested absolute structure of hygromycin and presented the existence of epihygromycin and its absolute structure [Journal of Antibiotics 33, 695 (1980)].
As regards the biological activity of hygromycin, this antibiotic is known to have strong inhibitory activity against gram-positive and gram-negative bacteria and acid-fast bacteria, especially human type tubercle bacilli, and has also been shown, by animal experiments, to produce therapeutic effects in infections caused by bacteria, inclusive of tubercle bacilli, Borrelia and certain viruses. However, it has not been suggested that hygromycin is effective against swine dysentery.